To create a new "Custom User Role":

• Login using an account that has 'Administrator' privileges.
• Click Settings on the top-right, and select Manage Users from the menu.
• In the resulting page, click  Create Custom User Role link under "Manage User Roles" section.
• In the resulting page, select desired "Scope of Access", and click "Next" button.
• In the page appears, define access privileges for this custom user role. Then click "Save" button.

Once you create a custom user role - you can assign it to one or more users as explained here.